With the rapid development of a wireless communication technology and the gradual popularization of a third generation wireless communication network technology, functions provided by a mobile terminal are more and more diverse. The mobile terminal generally implements a functional interface by a Universal Serial Bus (USB) composite device. The so-called USB composite device refers to a USB device in which a USB master device is provided with multiple sub-devices, and each sub-device communicates with a USB host side by multiple USB endpoints. Generally, these USB devices include: an Attention (AT) port for transmitting an AT command, a modem port for providing a data service function, and a sound port for transmitting audio data. If the mobile terminal has a storage function, the mobile terminal further is provided with a USB large-capacity storage device. Wherein, the USB host is generally a Personal Computer (PC) side device provided with a USB host controller.
The conventional sound port for audio transmission transmits data by bulk endpoints of the USB, the USB host controller will not reserve a transmission bandwidth for the bulk endpoints, and when the USB has a very heavy load, a data transmission real-time property of the sound port will be influenced to cause audio delay, worse tone quality, more noise and the like. In addition, due to a limited processing capability of a Central Processing Unit (CPU) of a mobile terminal, when large amounts of data are transmitted on the USB, a audio data transmission request from the USB host side will not be responded in time due to the exhausted internal bus bandwidth of the CPU, so that loss of the audio data is caused and thus the tone quality becomes worse.
Furthermore, the method for transmitting audio data by the sound port in the prior art is actually a method self-defined by a manufacturer and does not meet any USB standard, so that a mobile terminal is difficult to transplant an application in different operating systems and application scenarios.